反应详情

A stirred solution of 3α-acetoxy-5α-pregnane-11,20-dione (0.375 g.) in ethyl orthoformate (10 ml) at 0° was treated with 9 drops of 75% perchloric acid over 20 minutes. Ca 10 drops of pyridine were then added and the mixture was extracted with ice-cold ether. The organic layer was washed with N hydrochloric acid solution, then aqueous sodium hydrogen carbonate and finally water. It was dried (MgSO4) and evaporated. The residue (0.5 g) was purified by preparative t.l.c. (ethyl acetate/petrol, 1:3) and then crystallisation from methyl acetate/petrol to give the title compound (0.2 g), m.p. 150°-154°, [α]D - 59.8°, λmax. 258.9 nm (ε 15,900).

1. extractionthe mixture was extracted with ice-cold ether
2. washThe organic layer was washed with N hydrochloric acid solution
3. dry with materialIt was dried (MgSO4)
4. customevaporated
5. customThe residue (0.5 g) was purified by preparative t.l.c
6. custom(ethyl acetate/petrol, 1:3) and then crystallisation from methyl acetate/petrol